15 May 2023
Refrigeration below -100? (170 K) is often demanded in various industrial applications such as biomedicine,
food stocks, and semi-conductor processing. It is difficult to pump heat from 170 K to room temperature by a
single pure refrigerant in Joule-Thomson (JT) refrigerator due to the insufficient thermodynamic properties.
Mixed-refrigerants (MR) possess some attractive merit as an alternative for that temperature range. We select
the non-flammable refrigerants to avoid the operation safety issues such as flammability and explosiveness of
hydrocarbon refrigerants. This paper validates a possibility for obtaining 170 K by using a non-flammable
mixture refrigerant and determines its maximum COP. A two-stage cascade cycle is selected for design
simulation in order to achieve a high efficiency. In the main cycle, R14, R23, and R218 are used after we
consider the characteristics of the iso-thermal enthalpy difference. In addition, R410A, which is broadly used
in commercial refrigerators, is utilized in the precooling cycle. The optimal design and the operating condition
are evaluated with several parameters in the main and the precooling cycles, such as the suction and discharge
pressures of the compressors, the mass flow rate, the precooling temperature, and the MR compositions. The
simulation assumes the ideal conditions to analyze the performance of the cycle. Consequently, the maximum
COP is calculated at 0.78 when the mole composition of the ternary refrigerants (R14:R23:R218) is 0.7:0.1:0.2.